Management of device-to-device communication resources

ABSTRACT

A base station assigns a first set of device-to-device (D2D) communication resources to a first D2D group and assigns a second set of D2D communication resources to a second D2D group. The D2D communication resources of the first set are different from the D2D communication resources of the second set. The first set of D2D communication resources and the second set of D2D communication resources are subsets of reserved D2D communication resources which are a subset of defined uplink communication resources defined by a communication specification for uplink communication between the D2D UE devices and a base station where the reserved D2D communication resources not used for uplink transmission to the base station.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/105,451, filed Jun. 16, 2016 and entitled “MANAGEMENT OFDEVICE-TO-DEVICE COMMUNICATION RESOURCES,” which is a national stageapplication of PCT/US2014/071266, filed Dec. 18, 2014 and entitled“MANAGEMENT OF DEVICE-TO-DEVICE COMMUNICATION RESOURCES,” which claimspriority to Provisional Application No. 61/919,284, entitled “Schedulingfor D2D Communications” and filed Dec. 20, 2013, all of which areassigned to the assignee hereof and hereby expressly incorporated byreference in their entirety.

FIELD

This invention generally relates to wireless communications and moreparticularly to management of device-to-device (D2D) communicationresources.

BACKGROUND

Many wireless communication systems use base stations (communicationstations, transceiver stations, eNodeBs, eNBs) to provide geographicalservice areas where wireless communication user equipment devices (UEdevices) communicate with the base station providing the particulargeographical service area in which the UE devices are located. The basestations are connected within a network allowing communication links tobe made between the UE devices and other devices. The communicationsystem may include base stations that provide overlapping service areasof different sizes to serve various needs of mobile UE devices. Forexample, macrocell communications stations may provide macrocell serviceareas that are larger and may cover one or more small cell service areasprovided by small cell base stations.

In some circumstances, the communication links are between wirelesscommunication UE devices that are close to each other. In thesesituations, it may be preferred to have a direct communication linkbetween the two wireless UE devices rather than communicating through abase station. Such direct communication between devices is oftenreferred to as device-to-device (D2D) communication or peer-to-peer(P2P) communication. The communication resources (e.g., time frequencyblocks) used for D2D communication are typically a subset of thecommunication resources used by the communication system forcommunication between UE devices and the base stations.

An in-coverage (InC) UE device is a UE device that is within the servicearea of a base station and is capable of communication with the basestation. An out-of-coverage (OoC) UE device is a UE device that is notwithin a service area of any base station. D2D UE devices that areengaged in D2D communication with each other form a group. A D2D group,therefore, includes two or more D2D UE devices. There are five typicalcoverage scenarios that occur with D2D groups. In a first coveragescenario, all the UE devices of the D2D group are located in a servicearea of a single base station. For the first scenario, therefore, all ofthe D2D UE devices of the D2D group are InC UE devices in a singleservice area. In a second coverage scenario, none of the UE devices ofthe D2D group are located inside any service area of any base station.For the second scenario, therefore, all of the D2D UE devices of the D2Dgroup are OoC UE devices. In a third coverage scenario, at least one ofthe UE devices of the D2D group is located in a service area of a singlebase station and at least one D2D UE device of the group is outside allservice areas. For the third scenario, therefore, at least one of theD2D UE devices of the D2D group is InC UE device in a single servicearea and at least one UE device is an OoC UE device. The third coveragescenario is sometimes referred to as a partial coverage scenario. In afourth coverage scenario, at least one of the UE devices of the D2Dgroup is located within a first service area of a first base station andat least one D2D UE device of the group located within a second servicearea of a second base station. For the fourth scenario, therefore, atleast two of the D2D UE devices of the D2D group are InC UE devices indifferent service areas. In a fifth coverage scenario, at least one ofthe UE devices of the D2D group is located within a first service areaof a first base station, at least one D2D UE device of the group locatedwithin a second service area of a second base station, and at least oneUE device of the D2D group is an OoC UE device. For the fifth scenario,therefore, at least two of the D2D UE devices of the D2D group are InCUE devices in different service areas and at least one D2D UE device ofthe group is an OoC UE device. Other coverage scenarios are possible.Since the UE devices of a group are mobile, there are situations wherethe coverage scenario of a D2D group changes. For example, where onlyone UE device of a D2D group is in coverage and moves out of coverage,the coverage scenario changes from a partial coverage scenario to an outof coverage scenario.

SUMMARY

A base station assigns a first set of device-to-device (D2D)communication resources to a first D2D group and assigns a second set ofD2D communication resources to a second D2D group. The D2D communicationresources of the first set are different from the D2D communicationresources of the second set. The first set of D2D communicationresources and the second set of D2D communication resources are subsetsof reserved D2D communication resources which are a subset of defineduplink communication resources defined by a communication specificationfor uplink communication between the D2D UE devices and a base stationwhere the reserved D2D communication resources not used for uplinktransmission to the base station.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a communication system where macrocellcommunication resources are used for device-to device (D2D)communication.

FIG. 2 is a block diagram of the macrocell communication resources andthe D2D communication resources.

FIG. 3 is a block diagram of reserved OoC D2D resources having OoCpriority sets.

FIG. 4 is flow chart of a method of managing device-to-device (D2D)communication resources in a cellular system.

DETAILED DESCRIPTION

A communication specification defines macrocell communication resourcesfor communication between base stations (communication stations, eNBs,etc.) and wireless communication user equipment (UE) devices. Themacrocell communication resources include defined downlink communicationresources and defined uplink communication resources, both defined bythe communication specification. Downlink communication resourcesselected from the defined downlink communication resources that areassigned (scheduled) for downlink communication are referred to asscheduled downlink communication resources. Uplink communicationresources selected from the defined uplink communication resources thatare assigned (scheduled) for uplink communication are referred to asscheduled uplink communication resources. In accordance with embodimentsof the invention, some macrocell communication resources are reservedfor device-to-device (D2D) communication. These reserved resources arereferred to as reserved D2D communication resources. Although defineddownlink communication resources and/or defined uplink communicationresources can be used for D2D communication, only defined uplinkresources are used for D2D communication in the examples herein. Aportion of the reserved D2D communication resources is reserved forout-of-coverage (OoC) D2D communication and another portion is reservedfor in-coverage (InC) D2D communication. The portion of D2Dcommunication resources reserved for out-of-coverage (OoC) D2Dcommunication is referred to herein as OoC D2D reserved communicationresources and the portion reserved for in-coverage (InC) D2Dcommunication is referred to herein as InC D2D reserved communicationresources. For the example, all reserved D2D communication resourcesthat are not reserved for OoC D2D communication are reserved for InC D2Dcommunication. As discussed below in further detail, different sets ofInC D2D reserved communication resources are assigned to different D2Dgroups. Communication resource allocation information indicating theresource assignment is broadcast to all of the D2D UE devices within theservice area of the base station in some circumstances. In othercircumstances, communication resource allocation information istransmitted to at least one of the D2D UE devices of the D2D group. Forsome examples, the InC D2D communication resources are assigned to theD2D groups based on a priority level of the group. The priority levelsof the D2D groups can be obtained from the network and/or relayed to thebase station by one or more D2D UE devices. In some circumstances, a D2Dgroup may be in a partial coverage scenario where the D2D group includesat least one InC D2D UE device and at least one OoC D2D UE device. Insuch scenarios, the OoC D2D UE device(s) only transmit D2D signals usingselected OoC D2D communication resources selected from the reserved OoCD2D communication resources. The InC D2D UE devices transmit using theselected InC D2D communication resources selected from the assigned setof InC D2D communication resources. In some exceptional cases, a InC D2DUE device may use OoC communication resources. One advantage ofreserving D2D communication resources is that UE devices interested inreceiving D2D communication are able to monitor the signals moreefficiently.

FIG. 1 is a block diagram of a communication system 100 where macrocellcommunication resources are used for device-to device (D2D)communication. A base station 102 provides wireless communicationservices to wireless communication UE devices 103-109 within ageographical service area 110, sometimes referred to as a cell. Severalbase stations are typically interconnected through a backhaul to provideseveral service areas to cover large areas. The various functions andoperations of the blocks described with reference to the communicationsystem 100 may be implemented in any number of devices, circuits, orelements. Two or more of the functional blocks may be integrated in asingle device and the functions described as performed in any singledevice may be implemented over several devices. For example, at leastsome of the functions of the controller 112 may be performed by the basestation 102 and vice versa. A cellular communication system is typicallyrequired to adhere to a communication standard or specification. TheThird-Generation Partnership Project Long-Term Evolution (3GPP LTE)communication specification is a specification for systems where basestations (eNodeBs) provide service to wireless communication devices(user equipment (UE) devices) using orthogonal frequency-divisionmultiplexing (OFDM) on the downlink and single-carrierfrequency-division multiple access (SC-FDMA) on the uplink. Although thetechniques described herein may be applied in other types ofcommunication systems, the exemplary systems discussed herein operate inaccordance with a 3GPP LTE communication specification.

The base station 102 is a fixed transceiver station, sometimes referredto as an eNodeB or eNB, which may include a controller in somecircumstances. The base station 102 is connected to a controller 112within the cellular network 113 through a backhaul which may include anycombination of wired, optical, and/or wireless communication channels.For the examples herein, the controller 112 includes the functionalityof the Mobility Management Entity (MME) and the Packet Gateway (P-GW).Accordingly, the controller 112 includes a scheduler 114. In theexample, the scheduler 114 allocates time-frequency resources forcommunication between the UE devices 103-109 as well as between the basestation 102 and the UE devices 103-109. Wireless UE communicationdevices 116-118 outside of the geographic service area 110 are capableof receiving wireless service form the base station 102 when the devices116-118 are within the service area 110. Since, the devices 116-118,however, are out of range of the base station 102, communicationresources cannot be dynamically assigned or scheduled for the devices116-118 when they are outside of the service area 110.

The wireless (UE) communication devices 103-109,116-118 (collectively UEdevices) may be referred to as mobile devices, wireless devices,wireless communication devices, and mobile wireless devices, UEs, UEdevices as well as by other terms. The UE devices include electronicsand code for communicating with base stations and with other UE devicesin device-to-device configurations. The UE devices include devices suchas cell phones, personal digital assistants (PDAs), wireless modemcards, wireless modems, televisions with wireless communicationelectronics, and laptop and desktop computers as well as other devices.The combination of wireless communication electronics with an electronicdevice, therefore, may form a UE device. For example, a UE device mayinclude a wireless modem connected to an appliance, computer,television, or other device.

As explained above, in some situations, two or more UE devices maycommunicate directly with each other without communication through abase station. Such device-to-device (D2D) communication may occurbetween UE devices within the service area of a base station or outsidethe service area. For the example discussed herein, the in coverage(InC) D2D UE devices 104-109 are within the service area 110 andcommunicate with other D2D UE devices within the same D2D group usingD2D communication. Out of Coverage (OoC) D2D UE devices 116-118 areoutside of the service area 110 and communicate with each other usingD2D communication.

For the example of FIG. 1, the D2D UE devices are part of four D2Dgroups 121, 122, 123, 124. Although the first D2D group includes threeD2D UE devices 104, 105, 106 and the other D2D groups 122, 123, 124include two D2D UE devices, a D2D group can include any number of D2D UEdevices greater than one. Therefore, a D2D group includes at least twoD2D UE devices that communicate with each other using D2D communicationresources. A D2D group may be in an in-coverage (InC) scenario, partialcoverage scenario, or an out-of-coverage (OoC) scenario. The first D2Dgroup 121 and the second D2D group 122 in FIG. 1 are in the InCscenario. The third D2D group 123 is in a partial coverage scenariosince at least one D2D UE devices 109 of the D2D group 123 is within theservice area 110 and at least one D2D UE devices 117 of the D2D group123 is outside the service area 110. The fourth D2D group 124 is in theOoC scenario.

The base station 102 includes a wireless transceiver (transmitter andreceiver) that can exchange wireless signals with the UE devices 103-109within the service area 110. Transmissions from the base stations andfrom the UE devices 103-109 are governed by a communicationspecification that defines signaling, protocols, and parameters of thetransmission. The communication specification may provide strict rulesfor communication and may also provide general requirements wherespecific implementations may vary while still adhering to thecommunication specification. Although the discussion below is directedto the 3GPP Long Term Evolution (LTE) communication specification, othercommunication specifications may be used in some circumstances. Thecommunication specification defines at least a data channel and acontrol channel for uplink and downlink transmissions and specifies atleast some timing and frequency parameters for physical downlink controlchannels from a base station to a UE device.

A substantial portion of the macrocell communication resources are usedfor transmitting the downlink signals and the uplink signals. The basestation 102 transmits downlink signals to the UE devices 103-109 usingscheduled downlink communication resources of the defined downlinkcommunication resources defined by the communication specification andreserved for downlink communication. The UE devices transmit uplinksignals to the base station 102 using scheduled uplink communicationresources of the defined uplink communication resources defined by thecommunication specification and reserved for uplink communication. Themacrocell communication resources include frequency bands divided intime where each frequency band and segment of time can be identified bythe scheduler 114 and described in control signals sent from the basestation 102 to the UE devices 103-109. The communication specifications,or other system rules, therefore, define applicable communicationresources for the downlink and applicable communication resources forthe uplink. The scheduler 114 allocates different time-frequencyresources to different devices to efficiently utilize the resourceswhile minimizing interference. Accordingly, the scheduled macrocellcommunication resources used for signals exchanged with one UE deviceare different from scheduled macrocell communication resources used forother signals exchanged with other UE devices. As referred to herein,therefore, the defined macrocell communication resources are thecommunication resources reserved for communication by the specificationand/or communication system rules. The scheduled resources for macrocelltransmission for particular signals, however, are a subset of thereserved macrocell communication resources and are typically dynamicallychanged during operation.

In conventional systems, a scheduler allocates time-frequency resourcesfor communication between the base station and the UE devices. In theexamples discussed herein, however, the scheduler 114 also assignstime-frequency resources (D2D communication resources) for communicationbetween UE devices 104-109 to establish and maintain a device-to-device(D2D) communication link. For the examples herein, the scheduler and/orbase station 102 assign sets of reserved InC D2D communication resourcesto the D2D groups 121-124. The InC D2D UE devices select resources fromthe set of D2D communication resources assigned to the D2D group. OoC UEdevices, on the other hand, select resources from reserved OoC D2Dcommunication resources without dynamic scheduling or assignment by thescheduler.

For the example in FIG. 1, a first set of D2D communication resources ofthe reserved InC D2D communication resources are assigned to the firstD2D group 121 and a second set of D2D communication resources of thereserved InC D2D communication resources are assigned to the second D2Dgroup 122. In addition, a third set of D2D communication resources ofthe reserved InC D2D communication resources are assigned to the thirdD2D group. The Inc D2D UE devices select communication resources fromthe assigned set of resources for D2D communication. For the examples,the D2D UE devices select a resource by observing (listening) thecommunication resource to determine if another device is using theresource for transmission. The D2D UE device only selects and uses thecommunication resource if it is determined that the resource is notcurrently being used. The OoC D2D UE devices 116, 118 may selectresources from the reserved OoC D2D communication resources in a similarmanner.

For the examples herein, the D2D resources are selected by a basestation controller 126 at the base station 102. The base stationcontroller 126 may be part of the base station or connected to the basestation 102. The base station controller 126 communicates with thenetwork 113 and makes determinations regarding the appropriate resourcesto assign to D2D groups as well as performing other functions discussedherein. In some situations, the functions described as performed by thebase station controller 126 may be performed by other equipment orentities in the network 113 or the base stations. Further, functionsdescribed as performed by the base station 102 are performed by the basestation controller 126 in some circumstances.

FIG. 2 is a block diagram of the macrocell communication resources andthe D2D communication resources. The various blocks in FIG. 2 representsets of communication resources where a first block within a secondblock indicates that the first block includes communication resourcesthat are a subset of the second block. Communication resources may bedivided in frequency, time, and/or by coding. For the examples herein,the communication resources are time-frequency communication resources.Uniform single blocks do not necessarily indicate that all the resourceswithin the block are continuous in frequency and time. Therefore, ablock represents a collection of resources that may not be adjacent intime or frequency.

For the examples herein, a portion of the defined uplink communicationresources 200 are reserved for D2D communication. Some defined uplinkcommunication resources 200 are reserved for D2D discovery signaltransmission and are referred to as D2D discovery signal resources 202.Another portion of the defined uplink communication resources 200 arereserved for other D2D transmissions and are referred to as the reservedD2D communication resources 204. The reserved D2D communicationresources 204 include reserved InC D2D communication resources 206 andreserved OoC D2D communication resources 208.

The reserved InC D2D communication resources 206 provide a pool ofcommunication resources that can be scheduled (assigned) by thecontroller 112 to the InC D2D UE devices in the D2D groups 121, 122, 123for D2D communication within the service area 110. When the resourcesare assigned to a D2D group, they are referred to as assigned D2Dcommunication resources. For the example of FIG. 2, two sets of InC D2Dcommunication resources have been assigned. Accordingly, for theexample, the reserved InC D2D communication resources 206 include afirst set of assigned D2D communication resources 210 and a second setof assigned D2D resources 212. The first set of assigned D2Dcommunication resources 210 is assigned to one D2D group (e.g., thefirst D2D group 121) and the second set of assigned D2D communicationresources 212 are assigned to another D2D group (e.g., the second D2Dgroup 122). In situations where two groups are sufficientlygeographically separated, the same (or overlapping) communicationresources may be assigned to the two D2D groups.

When downlink communication resources are assigned for D2Dcommunication, those resources are not used for downlink communication.For example, if the communication resources are time-frequencycommunication resources, the time segments and frequency bands assignedto the D2D communication link are not used by the base station 102 toserve non-D2D wireless communication UE devices (104). Where uplinkcommunication resources are assigned for D2D communication, theresources are assigned such that communication between a group of D2Dwireless communication UE devices does not interfere with communicationsbetween any other D2D wireless communication UE devices in other groups.For example, orthogonal or nearly orthogonal, resources may be usedrelative to other nearby D2D device groups. D2D device groups that aresufficiently far from each other may be able to reuse communicationresources and avoid interference. For example, if the D2D devices ofeach group are relatively close to each other but the D2D groups arerelatively far from each other, the transmission power level used withineach D2D group may be sufficiently low to allow reuse of communicationresources within the same service area 110. The determination to reuseresources within the same coverage area 110 depends on the procedure forcontrolling transmission power of the D2D communication signals. Forexample, if the UE devices are transmitting at maximum power, theability to reuse resources for another group within the same coveragearea is significantly reduced or made impossible. In situations wherethe base station 102 has information regarding at least the generallocations of the UE devices for each D2D group, the base stationdetermines whether D2D groups are sufficiently apart to avoidinterference. The base station subsequently, specifies the maximumallowable transmission power when the D2D communication resources areassigned. Alternatively, the base station can allow the UE deviceswithin the same group to restrict their own transmit power based on thereceived power from other D2D UE devices within the D2D group.

In most situations, an InC D2D UE of a D2D group will request resourcesfor D2D communication from the base station 102. The request may includeinformation identifying the needs of the D2D communication link. Therequest may also include a Group ID of the D2D group to which the InCD2D UE belongs. The Group ID may provide additional information usefulfor determining the needs of the D2D group. For example, the Group IDmay be associated with a priority level which, as discussed below, mayat least partially dictate allocation of D2D communication resources. Inresponse to determining that a D2D connection should be established, thecontroller 112 allocates D2D time-frequency resources (allocated InC D2Dcommunication resources 210) to the D2D group 121. Therefore, inaccordance with the embodiments herein, some of the reserved Inc D2Dcommunication resources 206 are assigned for device-to-device (D2D)communication between two or more wireless communication UE devices asneeded.

In some situations, the allocation of D2D resources to the D2D groups isbased on a priority level of the D2D communication of the group.Priority levels establish relative importance or preference of thecommunication. For example, a high priority level can be associated withD2D groups establishing D2D communication for public safety where D2Dcommunication within a D2D group associated with commercial activitiesmay be associated with a lower priority level. Any number of prioritylevels may be employed depending on the particular implementation. Thecommunication resources assigned to a higher priority group may includemore resources than a lower priority group.

As an example, therefore, the first set of InC communication resources210 may be allocated to first D2D group 121 based on a priority level ofthe D2D group 121. The second set of InC communication resources 212 maybe allocated to second D2D group 122 based on a priority level of theD2D group 122. The priority level of a particular D2D group is typicallyestablished by the network 113. In some situations, the scheduler 114obtains the priority level of a group from the network 113. In othersituations, the base station 102 may obtain the priority level from a UEdevice within the D2D group and provide the priority level to thescheduler 114 to facilitate allocation of the D2D resources.

Any of numerous techniques may be used to inform the InC D2D UEs of thescheduled resources. One technique includes transmitting communicationresource allocation (CRA) information from the base station 102 to atleast one of the Inc D2D UE devices 106 in a D2D group after thecontroller 112 determines that D2D link communication should beestablished and determines the resources that should be allocated forD2D. In another example of allocating the InC D2D communicationresources 206, the base station 102 broadcasts a message identifying theset of assigned InC D2D communication resources 210 for use by the firstD2D group 121 and broadcasts a message identifying the second set ofassigned InC D2D communication resources 211 for use by the first D2Dgroup 122. An example of a suitable technique for broadcasting the CRAinformation includes transmitting the CRA information in _SystemInformation Block Type 18 for D2D communication and System InformationBlock Type 19_for D2D discovery transmissions. The broadcast informationshould also include the Group ID associated to an assigned resource.Alternatively, the CRA information may also be send to the InC D2D UEsusing dedicated signaling or more specifically, using aRRCConnectionReconfiguration message including proseDiscConfig orproseCommConfig. With the dedicated signaling, it is assumed that thebase station 102 would assign the same resources to all the InC D2D UEsbelonging to the same group. The UE devices within the D2D groups employa listen-before-transmit procedure in accordance with a Carrier SenseMultiple Access (CSMA) technique to identify the scheduled InC D2Dcommunication resources 210 that will be used by each particular group.

The InC D2D UE devices select resources from the assigned set of D2Dcommunication resources assigned to the D2D group. For the example,therefore, the D2D UE devices 104,105,106 select resources (selected D2Dcommunication resources 214) from the first set of assigned D2Dcommunication resources 210 assigned to the first group 121 and the D2DUE devices 107, 108 select resources (selected D2D communicationresources 216) from the second set of assigned D2D communicationresources 211 assigned to the second D2D group 122. The selected InC D2Dresources 214 may be distributed in several blocks within the assignedset of assigned D2D communication resources 210. In other words, theselected communication resources are not necessarily continuous set ofadjacent resources. Further, an assigned set of D2D resources 210 may bedistributed in several blocks within the reserved InC D2D communicationresources 206.

OoC D2D UE devices 116, 118 select communication resources form thereserved OoC D2D communication 108 without scheduling or assignment fromthe base station 102. The OoC D2D UE devices 116, 118 autonomouslyselect resources (selected OoC D2D communication resources 212) from thereserved OoC D2D reserved communication resources 208 using a techniquethat minimizes interference between other OoC D2D groups. A suitableexample for selecting resources includes employing alisten-before-transmit procedure in accordance with a Carrier SenseMultiple Access (CSMA) technique. Other methods can be used to determinewhich of the reserved OoC D2D communication resources will be used for aparticular OoC D2D group.

In some situations, the base station 102 may assign some of the OoC D2Dresources to InC D2D UEs. The OoC D2D UE devices 116, 118, however, canonly select resources from the reserved OoC D2D communication resources208 for transmission. In some circumstances where the base station 102has not scheduled or otherwise allocated D2D resources to the InC D2DUEs, the InC D2D UEs use reserved OoC D2D communication resources 208that are not selected OoC D2D communication resources being used by theOoC D2D UE devices. In some cases, the InC D2D UEs may only use the OoCD2D communication resources 208 if permitted by the base station 102.

The selected OoC D2D resources may be distributed in several blockswithin the reserved OoC D2D communication resources 208. In other words,a first set of communication resources selected by a first group of OoCD2D UE devices may be separated in time and frequency from a second setof communication resources selected by a second group of OoC D2D UEdevices. Further, the selected resources by any particular D2D group mayalso be separated within the reserved OoC D2D communication resources.

The third D2D group 123 is an example of a D2D group in a partialcoverage scenario. For the examples, the OoC D2D UE 117 of the grouponly uses selected OoC D2D communication resources 212 for transmittingD2D signals within the D2D group 123 and the InC D2D UE device 109 ofthe D2D group 123 transmits D2D signals using selected D2D communicationresources selected from the set of assigned D2D communication resources(not shown in FIG. 2). In some situations, the Inc D2D UE device 109uses OoC resources for transmission.

FIG. 3 is a block diagram of reserved OoC D2D resources 300 having OoCpriority sets 302, 304. For the example of FIG. 3, the reserved OoC D2Dcommunication resources are further organized into priority sets 302,304. Therefore, the reserved OoC D2D resources 300 is an example of thereserved OoC D2D resources 208 of FIG. 2 where the OoC resources areorganized into two priority sets 302, 304. In some circumstances, thepriority sets 302 and 304 are semi-statically assigned by the basestation 102. In other situations, the priority sets 303 304 are staticand are preconfigured. Additional priority sets can be used in somecircumstances. For the examples herein, the priorities are identified byGroup IDs. The Group IDs are associated with a priority level assignedby the higher layer such as the ProSe function or the D2D applicationlayer. The based station 102 obtains such information from the ProSefunction directly or through the UE devices if the D2D UE devices havesuch information. In other examples, the OoC D2D UE devices may selectresources from a priority set if the D2D communication priority level isequal to or greater to the priority level associated with the priorityset. As discussed above, priority levels are typically established bythe network 113. Since the OoC UE devices do not have access to thenetwork, priority levels established for types of D2D communication thelast time the UE device were in coverage are maintained for OoC D2Dcommunication. As discussed above, the priority levels are establishedsemi-statically and, as a result, the priority level informationmaintained at an OoC UE device is likely accurate. An example of asituation where OoC UE devices may have established priority levelsarises when some UE devices use the D2D resources of public safetypurposes and other OoC UE devices are using the D2D resources for otherpurposes such as D2D communication for commercial use. The UE devicesused for public safety may be assigned a higher priority level than theother UE devices. As a result, the UE devices not engaging in D2Dcommunication for public safety purposes are restricted to the secondpriority set of OoC D2D communication resources. The first priority setof OoC D2D communication resources are available to the public safety UEdevices. In some situations, the second priority set of OoC D2Dcommunication resources may also be available to the higher priority UEdevices.

Therefore the OoC D2D UE devices select resources from the priority setof D2D communication resources authorize for the UE devices based on theGroup ID and priority level assigned to the D2D group. Therefore, D2D UEdevices of a first priority select resources (selected D2D communicationresources 306) from the first priority set of D2D communicationresources 302 and D2D UE devices with second level priority selectresources (selected D2D communication resources 308) from the secondpriority set of D2D communication resources 304. The selected D2Dresources 306 may be distributed in several blocks within the firstpriority set of D2D communication resources 302.

FIG. 4 is flow chart of a method of managing device-to-device (D2D)communication resources in a cellular system.

At step 402, a first D2D group is identified. The first D2D groupincludes at least two D2D UE devices. For the examples the base station102 receives requests from UE devices for D2D communication resource.The requests identify the UE devices that will communicate with eachother using the D2D communication resources. The base station and/orcontroller associates the D2D UE devices with the first D2D group.

At step 404, a second D2D group is identified. The second D2D groupincludes at least two D2D UE devices.

At step 406, the a first set of D2D communication resources is assignedto the first D2D group and a second set of D2D communication resourcesis assigned to the second D2D group. The D2D communication resources ofthe first set are different from the D2D communication resources of thesecond set. As discussed above, the first set of D2D communicationresources and the second set of D2D communication resources are subsetsof reserved D2D communication resources which are a subset of defineduplink communication resources defined by a communication specificationfor uplink communication between UE devices and a base station. Thereserved D2D communication resources are not used for uplinktransmission to the base station.

The UE devices from the first D2D group select resources form the firstset and the UE devices from the second group select resources form thesecond set. A discussed above, a suitable method of selecting theresources includes using a listen then transmit technique such as CSMA.Accordingly, one or more UE devices of the first group select D2Dcommunication resources for the first set for D2D transmission at timesdetermined by the one or more UE devices. The UE devices transmit D2Dsignals using the selected communication resource only if adetermination is made than no other UE device is using the selectedcommunication resource. In some cases, a UE device only transmit D2Dsignals if it does not receive any D2D signal from another UE devicebelonging to the same group. The UE devices of the second D2D groupselect resources form the second set in a similar fashion.

For the examples, the controller 126 at the base station 102 assigns thesets of D2D communication resources to the D2D groups based on apriority level of the D2D communication of each group. For the examples,the priority levels are determined by the ProSe Function as specified bythe 3GPP LTE communication specification. The priorities are typicallyassigned semi-statically, and therefore, do not change frequently. Thepriority level of the D2D group is typically conveyed to the UE devicesusing the PC3 interface (IP protocol) although other techniques may beused. The controller 126 at the base station determines the prioritylevels from the D2D groups either by obtaining the information from theProSe Function or from the UE devices. Based on the information receiveddirectly from the network 113 or relayed by the UE devices, therefore,the controller 126 at the base station 102 determines a first prioritylevel for D2D communication between the UE devices of the first D2Dgroup and determines a second priority level for D2D communicationbetween the UE devices of the second D2D group. The base station 102then assigns the D2D communication resources based on the first prioritylevel and the second priority level. The communication resources can beconveyed to the UE devices by broadcasting the information or bydedicated signaling. In situations where the D2D UE devices have theGroup ID information, the base station 102 can broadcast onlyinformation identifying the D2D communication resources assigned to theGroup ID. The UE D2D devices can then determine which D2D communicationresources are assigned to the group in which they are communicating.

As discussed above, the reserved D2D communication resources includereserved in-coverage (InC) D2D communication resources and reservedout-of-coverage (OoC) D2D communication resources. The InC D2Dcommunication resources include the first set of D2D communicationresources and the second set of communication resources. The reservedInC D2D communication resources are reserved for D2D transmission by InCD2D UE devices that are within a service area of the base station andthe reserved OoC D2D communication resources are reserved for D2Dtransmission by OoC D2D UE devices that are outside the service area.

As discussed above, partial coverage scenarios can occur where a D2Dgroup includes one of more InC D2D UE devices located within the servicearea and one or more OoC D2D UE devices located outside the servicearea. In such situations, the InC D2D UE devices transmit D2D signalsusing the selected D2D communication resources within the assigned setof D2D communication resources and the OoC D2D UE device transmit D2Dsignals using only selected D2D communication resources selected fromthe reserved OoC D2D communication resources.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. The above description is illustrative and not restrictive.This invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and accompanying drawings. Thescope of the invention should, therefore, be determined not withreference to the above description, but instead should be determinedwith reference to the appended claims along with their full scope ofequivalents.

What is claimed is:
 1. A user equipment (UE) device in a cellularcommunication system comprising: a memory configured to store multiplesets of device-to-device (D2D) time-frequency resources, each of themultiple sets for which a resource priority is preconfigured; and acontroller configured to perform D2D communication within a D2D groupincluding the UE device, wherein the controller is further configuredto, when the UE device is out of coverage, perform the processes of:identifying a communication priority of the D2D group; selecting a firstset of D2D time-frequency resources from the multiple sets, the firstset having a resource priority corresponding to the communicationpriority; selecting a part of the first set as D2D time-frequencyresources used for the D2D communication.
 2. A method performed at auser equipment (UE) device in a cellular communication system, themethod comprising: storing multiple sets of device-to-device (D2D)time-frequency resources, each of the multiple sets for which a resourcepriority is preconfigured; when the UE device is out of coverage,identifying a communication priority of a D2D group including the UEdevice; selecting a first set of D2D time-frequency resources from themultiple sets, the first set having a resource priority corresponding tothe communication priority; selecting a part of the first set as D2Dtime-frequency resources used for D2D communication; and performing theD2D communication with the part of the first set within the D2D group.3. An apparatus for controlling a user equipment (UE) device in acellular communication system comprising: a memory electricallyconnected to a controller; and the controller, wherein the controller isconfigured to perform the process of: storing multiple sets ofdevice-to-device (D2D) time-frequency resources, each of the multiplesets for which a resource priority is preconfigured; when the UE deviceis out of coverage, identifying a communication priority of a D2D groupincluding the UE device; selecting a first set of D2D time-frequencyresources from the multiple sets, the first set having a resourcepriority corresponding to the communication priority; selecting a partof the first set as D2D time-frequency resources used for D2Dcommunication; and performing the D2D communication with the part of thefirst set within the D2D group.